AU605110B2

AU605110B2 - Aluminum bearing alloy and two-layer bearing material having bearing layer of aluminum bearing alloy therein

Info

Publication number: AU605110B2
Application number: AU62602/86A
Authority: AU
Inventors: Masahito Fujita; Akira Ohgaki; Toshinaga Ohgaki; Tsuyoshi Ohsaki; Takeshi Sakai
Original assignee: NDC Co Ltd; Nippon Dia Clevite Co Ltd
Current assignee: NDC Co Ltd
Priority date: 1985-09-13
Filing date: 1986-09-11
Publication date: 1991-01-10
Anticipated expiration: 2006-09-11
Also published as: KR900007784B1; DE3631029A1; GB2182348B; AU6260286A; GB8621417D0; US4789607A; GB2182348A; DE3631029C2; KR870003223A

Description

ii_ i: II I S60511 0 COMMONWEALTH OF AUSTRALIA PATENT ACT 1952 COMPLETE SPECIFICATION (Original) FOR OFFICE USE Class Int. Class Application Number: Lodged: 626o21S6 Complete Specification Lodged: Accepted: Published: Priority: .Related Art: arnendm1nts rl rid; I iflOr iS L f M;

I

see*

OOS*

*6

S.

*0 of Applicant: Address of Applicant: Actual Inventor(s): Address for Service: Address for Service: NDC COMPANY, LTD.

1-687, Mimomi-cho, Narashino-shi, Chiba-ken,

JAPAN.

Masahito FUJITA Akira OHGAKI Takeshi SAKAI Toshinaga OHGAKI Tsuyoshi OHSAKI DAVIES COLLISON, Patent Attorneys, 1 Little Collins Street, Melbourne, 3000.

Complete Specification for the invention entitled: "ALUMINUM BEARING ALLOY AND TWO-LAYER BEARING MATERIAL HAVING BEARING LAYER OF ALUMINUM BEARING ALLOY THEREIN" The following statement is a full description of this invention, including the best method of performing it known to us -1- *1

I

ALUMINUM BEARING ALLOY AND TWO-LAYER BEARING MATERIAL HAVING BEARING LAYER OF ALUMINUM BEARING ALLOY THEREIN BACKGROUND OF THE INVENTION Field of the Invention This invention relates to a two-layer Al bearing material consisting of an Al bearing alloy layer and a backing metal consisting of a steel sheet or the like.

More particularly, the invention concerns an Al bearing alloy, which contains Sn and Pb as well as Si, and 4wh-c-h-S-i-i-s-p yi-p-i-.t-a-t-ed-a-s-Si -prcipi-t-a-tc particles having spherical or nearly spherical shape in an Al matrix and also Sn-Pb alloy pa'rt-i les are precipitated in the vicinity of the Si p-.eci i ta n t at ih t .las h 15 /,improved fatigue-resistant property, anti-seizure property and abrasion-resistant property under high W e speed, high load running conditions of the autombile, S. and also a bearing material consisting of the Al bearing alloy and backing metal.

Prior Art Recently, there are trends for smaller size, lighter weight, lower fuel consumption and higher output of automobile engines. Therefore, the bearing should bear increased load, and also the operating temperature of lubricant is increased. The operating conditions of the bearing thus are becoming increasingly stringent.

Generally, the bearing has a three-layer structure consisting of a backing metal formed from a steel plate 1A- I. 0 4 .4 INKI or the like, an Al bearing alloy layer formed on the backing metal and a bearing layer formed by means of overlay plating on the Al bearing alloy layer. The bearing of this three-layer structure consisting of the backing metal, bearing alloy layer and overlay plating bearing layer, however, is subject to fatigue or seizure due to temperature elevation of the bearing surface, so that it can not meet the stringent operating conditions noted above. Accordingly, there has recently been a demand for a bearing having a two-layer structure, which does not have any surface bearing layer of overlay plating but supports an engine shaft with a bearing alloy layer formed on a backing metal. At present, however, a bearing having stable performance can not be obtained S 15 even by adopting the two-layer bearing structure because Al bearing alloys that have been developed so far can *insufficiently meet the stringent operating conditions noted above.

*1*r More specifically, in the three-layer bearing having a surface bearing layer formed by overlay plating the intermediate bearing alloy layer consists of such an Al bearing alloy as JIS (Japanese Industrial Standards) H trbS :5402, AJ-1 (10% Sn, 0.75% Cu, 0.5% Ni, Al as balance), or JIS H 5402, AJ-2 Sn, 2.5% Cu, 1.0% Ni, Al as balance) 25 or such Al bearing alloy as SAE 780 Sn, 2% Si, 1% Cu, e* 0.5% Ni, 0.1% Ti, Al as balance), and its Sn content is comparatively small, typically 10 to For this reason, a Pb-Sn alloy layer is formed as surface bearing 2 ~F7" ~~~arxl~r r ~~aa d~c layer by overlay plating.

However, under recent high load, high temperature operating conditions, the surface bearing layer is worn out to result in seizure so that it can no longer withstand use in a comparatively short period of time.

With the two-layer bearing having overlay plating layer as surface bearing layer, on the other hand, the bearing alloy layer is, for instance, SAE 783 (20% Sn, 0.5% Si, Cu, 0.1% Ti, Al as balance) or like Al alloys with as high Sn content as 20%. Since the Sn content is high, however, the hardness is reduced, and the Al matrix is fragile, so that the bearing can not withstand high load.

In "Jiku-uke Gokin" (Bearing Alloys) by Koichi Mizuno, published by Nikkan Kogyo Shinbun Sha, issued in Pfcoe.OSa 1954, pp. 139 it is sdi loseQdto form a bearing alloy layer from a bearing alloy, which has enhanced antiseizure property provided by increasing the lubrication property with addition of Pb together with Sn. This bearing alloy contains 10% of Sn, 1.5% of Cu and 0.5% of Si and also 3% of Pb. Therefore, it can not withstand the high load as noted above although the lubrication property can be improved to some extent.

An Al alloy which contains Sb incorporated to improve the dispersion of Pb which hardly forms a solid solution with Al, is disclosed in Japanese Patent Publication No. 121, 131/1977. Further, a. Al alloys containing Cr added for Al matrix reinforcement and also for preventing coarse Sn particles are disclosed in

S

5.

S

0 5555

SO

S*

S. S 3 I* -i Japanese Patent Publication No. 18,985/1983. These Al alloys, however, have been developed for the purpose of improving the ihrj1arnf-rn jroperty under ordinary running conditions, and they do not exhibit sufficient anti-fatigue property under high load running conditions, under which the lubrication mechanism is quite different from that under the ordinary running conditions.

To meet the lubrication mechanism under high load running conditions, there has been proposed a bearing alloy, which is obtained by adding a large quantity re-, 11% or above, of Si to a Sn-containing Al alloy so that it has dispersed Si precipitates which are coarse in grain and have 1 w.p This bearing alloy is imparted with forging property and creep property by the addition of a large quantity of Si. In addition, the cutting force provided by hard Si precipitate particles has an effect of removing irregularities of the counterpart rotary shaft surface to eeoc o.O provide a smooth surface, thus improving the performance 20 of the bearing. More specifically, the surface of a rotary shaft made of spherical graphite cast iron or the like has depressions, which result from detachment of graphite particles at the time of polishing, and raised

S.

portions such as burrs or edges formed around the 25 recesses. Under high load running conditions, the 0S surface of the bearing alloy layer is ground by such recesses and raised positions of the rotary shaft, thus resulting in abnormal wear of the bearing. With the 4 M t. II ibearing alloy having dispersed Si precipitate particles the raised portions of the shaft surface are cut away by the hard Si precipitate particles, thus preventing abnormal wear or seizure.

In order to cut the counterpart shaft surface with the Si precipitates to improve the anti-seizure property, it is necessary to add as large amount of Si as 11% or above. The addition of such large amount of Si, however, rather leads to damage to the shaft surface because of precipitation of coarse Si particles. It also leads to cause seizure and deterioration of the cutting or like machining property because of lack of ductilities of the alloy, which is a serious problem. To cope with these problem there has been proposed a bearing alloy, in which the Si content is reduced to be less than 11S, particularly to 0.2 to as disclosed in Japanese Patent Publication No. 6.955/1983. With this bearing alloy, however, it is impossible to attain improvement of the anti-seizure property due to cutting force of Si 20 precipitates as noted above under high load running conditions, and an improvement in this respect has been called for.

SUMMARY OF THE INVENTION According to the invention, there is provided a 25 predominantly aluminum alloy composed of, in addition to Al and any impurities, 3 to 35% w/w Sn, 0.5 to 10% w/w Si, 0.1 to 10% w/w Pb, at least one member of the group consisting of 0.01 to 0.3% w/w Sr and 0.01 to 0.3% w/w Sb and, optionally, 0.1 to 4% w/w in total of at least one member of the group consisting of Cu, Mg, Zn, Cr, Mn, Fe, Ni, Co, Mo, Ti, V and Zr, at least part of said Si being dispersedly precipitated in a matrix consisting substantially of Al as Si precipitate particles having spherical or oval shape or a shape having rounded ends and projecting from the surface of the matrix, said Sn ,O and Pb being precipitated as Sn-Pb alloy precipitate in r) the matrix adjacent to said Si precipitate particles.

900918,phhspe.008ncjspe,5 4 -6- Further according to the invention there is provided a two-layer aluminum bearing material comprising a predominantly aluminum alloy as described in the immediately preceding paragraph a backing metal sheet of, for example, steel or stainless steel.

Where both Si and Sb are present in the alloy, they are preferably present in an amount totalling no more than about 0.3% w/w.

S. All of the proportions hereinafter are given by 10 weight.

s .BRIEF DESCRIPTION OF THE DRAWINGS One embodiment of an alloy in accordance with the invention will now be described by way of example only eg*.

with reference to the accompanying drawings, in which: Figure 1 is a fragmentary enlarged-scale sectional view showing an embodiment of the bearing material and a too*part of rotary shaft of bearing mechanism according to the invention; ~Figure 2 is a fragmentary enlarged-scale sectional view illustrating a state of lubrication of a prior art three-layer structure bearing material; Figure 3 is a fragmentary enlarged-scale sectional view showing a prior art two-layer structure bearing material and a part of a shaft of bearing mechanism with 25 a comparatively high content of Si; Figure 4 is a fragmentary enlarged-scale sectional view illustrating a state of lubrication of the bearing material shown in Figure 3; Figure 5 is a fragmentary enlarged-scale sectional view illustrating a state of lubrication of the bearing material shown in Figure 1; Figures 6 and 7 are views showing microscopic structure 9 h n 900918,phhspe.008,ndcrspe 6 of a bearing alloy of the bearing material as shown in Fig. 1; and Fig. 8 is a view showing the microscopic structure of a bearing alloy of the bearing material shown in Fig. 3.

DESCRIPTION OF THE PREFERRED EMBODIMENT Referring to Fig.l, reference numeral 1 designates a bearing alloy according to the invention. The bearing alloy 1 is a forged Al alloy containing 3 to 35% of Sn, 0.1 to 10% of Pb and 0.5 to 10% of Si, the balance being substantially Al. This alloy has Al matrix 2 mainly composed of Al (hereinafter referred to as Al matrixes).

In the alloy, Sn and Pb are precipitated in the Al matrixes 2 as Sn-Pb alloy precipitate, Sn-Pb alloy 3 particles. In addition, Si is partly or totally precipitated as Si precipitate particles 4, which have a spherical or -".yspherical shape or a shape having round ends. With the alloy having this structure, a rotary shaft 5 which is supported by the surface of this 0 S.alloy is actually supported by round ends 4a of nearly 20 spherical Si precipitate 4. This support thus is the ideal point contact support, so that the lubrication property and fatigue-resistant property can be enhanced eeoc to prevent the surface temperature from increasing.

Besides, with the spherical shape of the Si precipitate 4 S. 25 mainly the tenacity of the Al matrix can be improved in the structural aspect.

In order to improve the sole anti-fatigue property ge.cit under a high temperture condition, it may be thought to Beo 7 II~L~c*un-- ~lxra*m~rr~~m*LI~ add such high-melting elements as Cr, Co and Ni to increase the high temperature strength and prevent sharp reduction of the hardness with temperature rise. While the hardness of the alloy can be increased by adding these high-melting elements, the alloy in this case becomes fragile, that is, the tenacity thereof is reduced to reduce impact value and elongation. To solve this problem, according to the invention at least one member of a group consisting of Sr and Sb is added to alloy containing Si as well as Sn and Pb. The added Sr and/or Sb control the liquid phase of Al alloy at the time of the solidification and permit precipitation of Si in a spherical form. It is thus possible, if desired, to enhance the roundness of the Si precipitate even where 15 heat treatment is conducted under ordinary heat treatment conditions, thus obtaining increase of tensile strength, elongation and impact strength of Al-Sn matrixes.

A more detailed discussion will be given in this connection. The anti-fatigue strength of material 20 depends on the tensile strength, elongation impact strength and structure of the material, and problems in this connection can not be solved by merely adding a high-melting element as in the prior art case. The inventors have conducted extensive researches and investigations in this connection. They have found that the addition of 0.01 to 0.3% of Sr or 0.01 to 0.3% of Sb permits precipitation of Si in spherical shape to greatly improve the mechanical properties such as tensile *I 9 9*9* 8 i i

I

strength, elongation and impact strength of the Al matrix just like spherical graphite cast iron has greatly improved mechanical properties compared to flaky graphite cast iron. This feature is supported by the fact that improvement of the fatigue strength is recognized as a result of fatigue tests under high temperature, high load conditions.

Further, the spherical shape of the Si precipitate 4 is improved such that the surface structure of the bearing surface meets the high temperature, high load conditions. This permits extreme improvement of the surface performance, anti-seizure property and lubrication property.

The phenomenon of seizure usually takes place through a complicated process and due to a combination of ia large number of different factors. Thr..for, .the **to d if-fi cu 1 1- q gra p i Gfin-'y-. However, while with a three-layer structure *bearing material having a surface bearing layer of a Pb- 20 Sn alloy or the like formed by overlay plating the bearing layer is worn out to result in seizure under high temperature, high load running conditions, seizure frequently will not result with a two-layer bearing material, which is made of an Al alloy with a 25 comparatively high Si content as bearing alloy but does not have any surface overlay plating bearing layer.

The inventors have noted this fact and made structural comparative study of both the bearings. Fig.

S

9 i II 'I" 2 is a fragmentary enlarged-scale sectional view showing the three-layer structure bearing material. Referring to the Figure, the material comprises a backing metal 6 made from a sheet or the like, a bearing alloy layer 7 formed on the backing metal 6 and a bearing layer 8 formed by overlay plating on the bearing alloy layer 7. Figure 3 is a fragmentary enlarged-scale sectional view showing a two-layer bearing material with high Si content. More go f specifically, this material comprises a backing material 6a made from a steel sheet and an Al bearing alloy layer with Al matrix 10. This material is free from any overlay plating bearing layer. With the three-layer bearing material of Figure 2 the load of rotary shaft is supported by the entire surface of the overlay plating bearing layer 8. Between the rotary shaft 5 and the bearing layer 8 there is existing lubricant 9 and via the intervening lubricant 9 the rotary shaft 5 is supported by plane-contact support.

so: On the other hand, with the two-layer structure bearing material Si is precipitated as Si precipitate particles 11 having rod-like or flaky shape in the bearing alloy layer, and the load of shaft 5 is supported *by these Si precipitate particles. In other words, with the two-layer bearing material shown in Figure 2, by 25 which the shaft load is supported by the plane contact support, under high speed, high load conditions the temperature of the frictional surface is quickly elevated so that the bearing layer 8 of a Pb-Sn alloy, for instance, is worn 90918,phhspP_008,ndr~sM1O

.I-I

out. In this case, if the lubrication property of the bearing alloy 7 inferior to that of the bearing layer 8, the lubrication property is quickly reduced to result in seizure. On the other hand, with the three-layer bearing material shown in Fig. 3 the shaft load is supported by point-contact support. Therefore, a slight gap 12 is formed between the surface of the bearing alloy layer the Al matrixes thereof, and the surface of the rotary shaft 5. A lubricant, therefore, is thus found in the gap 12. The lubricant film is held in the gap 12.

The lubricant film is not broken since it does not bear substantially high load, so that temperature rise of the frictional surface is suppressed.

As discussed above, with the two-layer bearing material shown in Fig. 3 the shaft load can be supported by point-contact support by the Si precipitate particles •in the Al matrix of the bearing alloy layer. With this .structure, however, the Si precipitate particles 11 are S' flaky or rod-like and have edges 11a, which will rather S. 20 cause scars and scratches to the surface of the shaft.

Seizure, therefore, is liable. Further, if the Si precipitate is excessive, the machining property is S deteriorated.

More specifically, Si is a stable substance having 25 high melting point and has a strong non-metallic character. Therefore, even if the bearing material shown in Fig. 3 is in contact with steel as surface material of S"the supported shaft in a high temperature condition of 11 ~ta~l~~uaurr~o~rm~r~p^i nehe 200 to 500 0 C, ijt-e reaction with Fe nor dispersion nor dissolution will occur. For this reason, the load of the rotary shaft is supported by the Si precipitate in the manner as described above. Further, the Si precipitate is as hard as 599 in Vickers hardness, and also usually it is not a compound but consists of Si alone, it is not h;B fragile and has rig. elasticity. Thus, the material can withstand sudden changes in the load even where the rotary shaft is supported via the intervening lubricant film. Therefore, the bearing material shown in Fig. 3 has excellent beazing performance compared to high temperature, high load conditions compared to other bearing materials, the bearing material shown in Fig. 3.

In spite of the fact that Si has the above character, it has a strong trend of crystallization.

Therefore, the Si precipitate has a plate-like or rodlike shape even in case when it is in eutectic precipitate with Al. The shape undergoes only slight change even when rolling and heat treatment processes are performed during manufacture of the bearing. Therefore, if no control of the status of the Si precipitate particles is done, 4 kis precipitated as plate-like or rod-like Si precipitate particles 11 in the Al matrixes 10. Where Pb and Sn are contained, Sn-Pb alloy particles 3 are formed by precipitation at positions spaced apart from the Si precipitate particles 11 i. the Si precipitate particles are plate-like or rod-like. In 12 6 6 S

S.

6* a S .5 *n 5

S

.1

E

0' J Y* 0

C.

A a C Cr 6 I 60

C'.

b Se d6006~ $i 0 this case, the surface of the supported shaft 5 is ground and damaged by the edges 11 a of the hard Si precipitate particles 11. When this cutting proceeds, seizure eventually results.

For the above reason, according to the invention, Si is precipitated, and the lubrication property oI' the Si precipitate is utilized. To remove the cutting force of the Si precipitate, the shape of the Si precipitate is controlled such as to provide for roundness of shape of the Si precipitate particles, spherical shape thereof. At the same time, Sn-Pb alloy precipitate particles are dispersed around the Si precipitate particles.

More specifically, according to the invention, Si 15 precipitate particles 4 are dispersed in the Al matrix 2 as shown in Fig. 1, while the shape of the Si precipitate particles 4 are rendered to be spherical by the addition of Sr and/or Sb. Thus, while the rotary shaft 5 is supported in point-contact support by the spherical Si precipitate particles 4, no scars or scratches are caused to the surface of the rotary shaft 5 even if the bearing experiences suddenly changing loads.

Further, since the Si precipitate 4 is found as spherical particles in the Al matrix 2, there will occur no notch effect. Thus, it is possible to obtain a matrix having a stable mechanical strength and excellent abrasion-resistant property.

The spherical shape of the Si precipitate particles 13 1: i i i i 9 i_ _I r"i -14 4 can be attained by improving the character of the Al alloy liquid phase at the eutectic point, at which Si is precipitated. Particularly, effective improvement of the character of the Al alloy liquid phase can be obtained by adding at least one member of a group consisting of 0.01 to 0.3% of Sr and 0.01 to 0.3% of Sb.

More specifically, by adding Sr and/or Sb in the ranges noted above, the dispersion of the Si precipitate S".particles 4 is improved, and also spherical shape of Si 10 precipitate 4 can be obtained. Further, the status of precipitation of Sn-Pb alloy particles 3 is changed, that is, the Sn-Pb alloy particles 3 precipitated is found closer to the spherical Si precipitate particles 4, as shown in Figures 1 and Figure 5 shows an enlarged-scale sectional view of the surface of the bearing alloy layer of the surface of the bearing material having the structure as shown in Figure 1. The shaft load is supported by end portions 4a of Si precipitate particles 4 projecting from the surface of the Al matrix 2. In addition, there exists a lubricant film 13 between the surface la of bearing alloy layer 1 and rotary shaft 5 (see Figure Thus, fluid lubrication is maintaird. Further, the Sn-Pb alloy particles 3 are present in the neighborhood of the Si 25 precipitate 4. This alloy has a strong affinity with the lubricant of the lubricant film 13. Therefore, breakage of the lubricant film at the end portions 4a of precipitate particles 4 occurs only with difficulty.

Further, even when the Si 900918,phspe.008,ndcspe,4 n precipitate 4 is elevated in temperature due to its friction with the rotary shaft 5, the heat can be absorbed as heat of melting of the Sn-Pb alloy particles 3, so that there occurs less seizure between the neighboring Al matrix and rotary shaft. Further, even if the Sn-Pb alloy particle 4 adjacent to the Si precipitate 4 as shown in Fig. 5 is at least partly in liquid phase, this liquid phase 3a is supplied to the projecting surface 4a of the Si precipitate 4 to keep the lubrication. The amount of the liquid phase 3a supplied is increased with temperature rise under the boundary lubrication, and the Sn-Pb liquid phase 3a is present on the surface 4a of the Si precipitate 4 at all time, so S 5 that the lubrication can be kept and it is possible to oto prevent metals from adhering one another. The structure, fees in which the Si precipitate particles 4 are spherical and Sn-Pb alloy particles 3 are found close to the Si precipitate 4, is extremely effective in an interface lubrication state a state of absence of lubricant film). Further, even in the ordinary fluid lubrication state the hard Si precipitate 4 adequately adopts itself to the rotary shaft 5, and the Si precipitate 4 is adjacent to soft Sn-Pb particles which serves as shock absorber.

Further, it is preferred to enhance the mechanical strength of the matrix at high temperature in addition to improving the bearing alloy layer surface performance.

More specifically, Al as main component of the Al matrix 15 0

I-

I

16does not endure high temperature, and when the temperature exceeds 150°C, it is softened (with Hv becoming 10 or below), and its mechanical strength is lost. As Al matrix reinforcement element of precipitation hardening type, Cu, Mg, Zn, Mn, Fe, Co, Ni, Mo, Ti, V, Zr, etc. can be added. If one or more of these reinforcement elements are selected, and appropriate heat treatment is performed, the mechanical strength at high temperature can be further increased.

S9 10 The adequate total amount of these additional elements is 0.1i to When the elements are added in this range, .9.9 they will impart the bearing with an anti-fatigue property. Addition of elements in excess of this range will result in size increase of the precipitate, and the tenacity is deteriorated.

The reasons for the limitation to the content of the *f components in the bearing alloy layer are follows.

Sn to 3 to Sn is present in a dispersed state in the Al matrix and provides for anti-seizure property which is a basic property required for the bearing material. Sn also helps to reduce a possibility that obstacles such as dust, dirt, etc. bury into the bearing surface, resulting in improving the lubrication performance between the bearing surface and rotary shaft. In addition, it is alloyed with Pb to be precipitated as Sn-Pb alloy particles to attain the above effect. However, when its content is less than the anti-seizure property and other properties, e.g. precipitation of Sn-Pb particles in the vicinity of the Si precipitate, which is attributable to the addition of Sr and/or Sb according to the invention, can not be obtained. When its content exceeds 35%, on the other hand, the mechanical strength of the Al matrix is deteriorated, even by adding the aforementioned optional Al matrix reinforcement elements.

Pb to 0.1 to Pb helps to improve the anti-seizure property, N ,phbsp&OO8,ndcqsc,16

I

q 17- J. p S. P

P

p.

p S affinity to oil and agglomeration-free property. Pb also helps to reduce a possibility that obstacles such as dust, dirt, etc. bury into the bearing surface, resulting in improving the lubrication performance between the bearing surface and rotary shaft. It is alloyed with Sn to be precipitated as Sn-Pb alloy particles to provide the effects noted above, thus outstandingly improving the lubrication performance. Its content should be determined in relation to the content of Sn. When the Sn 10 content is at least 0.1% of Pb is necessary.

However, when Pb is added in excess of 10%, it frequently fails to form solid solution with Sn but is precipitated alone. In this case, it is practically impossible to obtain uniform dispersion of Pb for Pb will not form solid solution with Al.

Si to 0.5 to Si is precipitated as Si precipitate as noted above, and it is an important element in that it provides for anti-seizure property, load resistance and abrasionresistant property. However, when its content is less

P

Ph P. P P 9oo918,phhspe.8,ndspe,17

I

9* 9 0 -5 1 than improvement of the mechanical characteristics of alloy due to provision of the spherical shape of the Si precipitate or improvement of the lubrication property can not be recognized. When its content is above 10%, on the other hand, it is difficult to provide for the spherical shape of its precipitate particles even by adding Sr or Sb. Rather, large size plate-like or rodlike precipitate particles are increased. In this case, the hardness of the Al matrix is increased, and the ductility and machining property are lost. The processing property of the bearing material is deteriorated, and the anti-fatigue property is deteriorated due to extreme hardening of the bearing alloy. Thus, the load resistance is rather deteriorated.

One or more members of a group consisting of Cu, Mg, Zn, Cr, Mn, Fe, Ni, Co, Ti, V and Zr to 0.1 to 4% in total: Cu, Mg and Zn are basic Al matrix reinforcement elements, and their effect can be obtained by appropriate heat treatment. If their content is less than no effect of addition can be obt-in-3d. If their content exceeds on the other hand, they form compounds with Al, so that they rather teterioratesthe ductility of the material.

Cr, Mn, Fe, Ni, Co, Ti, V and Zr form compounds with Al. The hardness and mechanical strength of the Al matrix can be increased by slightly adding it. These elements can substitute for part of Cu, Mg and Zn.

18

Y

i-) bt0, -19- Further, the anti-fatigue property, abrasion-resistant property and mechanical strength at high temperature can be improved by adding them in adequate amounts. Their suitable amount is 0.001 to 1.0% when Cu, Mg and Zn are 0.3 to If the amount is above the size of compound particles is increased. In this case, the mechanical strength of the alloy is rather reduced.

Sr to 0.01 to 0.3% and/or Sb to 0.01 to 0.3%: Sr and Sb cause dispersed precipitation of Si as 10 precipitate particles having spherical or oval shape or a shape with round ends. This effect can be obtained when either one of these elements is added, but the effect can be enhanced when both the elements are added together.

To obtain this effect, most preferably the content of Sr is 0.01 to 0.3% and/or the content of Sb is 0.01 to 0.3%.

When Sr or Sb is less than 0.01%, it will have no influence on the shape of the Si particles. When Sr or *f Sb is added by more than spherical shape of Si precipitate can no longer be obtained. Besides, Sb is precipitated in the Sn phase as a compound so that it is not useful for the improvement of the Si precipitate shape. When the Sr content exceeds a gas absorption takes place to form nestles during the forgoing.

Examples of the invention are given below.

EXAMPLE 1 Al bearing alloys having compositions shown in Table 1 were used for continuously forgoing plates with a thickness of 20mm. The upper and lower surfaces of each -'1 ba o ur 900918,phhspe.08,ndc.spe,19 -1

I

S. *9

S

*5 9 S S

S.

S..

S,

billet forged were cut away by 0.1 mm, followed by cold rolling to a thickness of 2 mm. The resultant sheet was heated to 300 to 350 °C and then cooled down, thus obtaining a bearing alloy layer. The bearing alloy layer was then press bonded to a steel sheet base member via a thin Al sheet, thus obtaining a bearing material 1.50 mm in thickness and having a two-layer structure consisting of backing metal and bearing alloy layer. The thin Al sheet was used for bonding the steel sheet and bearing alloy layer to each other. Similar press bond could be obtained by forming an Al plating sheet in lieu of the thin Ni on the surface of the backing metal.

Of the bearings Samples No. 1 to No. 5 were contrast samples not containing Sr. Sample No. 4 contained a great amount, of Sb. Samples No. 6 to No. 49 were according to the invention. Among these samples, Samples No. 19, No. 26, No. 27, No. 31 and No. 33 contained both Sr and Sb to provide for spherical shape of the Si precipitate. Samples No.35 to No. 49 contained only Sb to the same end. Samples No. 7 to No. 12 further contained Cu, Mg and Zn. Samples No. 13 to No. 19 contained Cr, Mn, Fe, Co, Ni, Mo and Sb, respectively, these elements being added to the composition of Sample No. 6. Further, these samples slightly contained Ti added to the end of crystal grain size reduction.

Samples No. 20 to No. 34 contained suitable combinations of these additive elements. Samples No. 35 to No. 41 contained Sb added for providing for spherical shape of 20 i, Si particles and also contained Cu added for enhancing the mechanical strength of the Al matrix. These samples also contained Cr, Mn, Fe, Co and Ni, respectively, and also slightly contained Ti added for crystal grain size reduction. Samples No. 43 to No. 49 contained suitable combinations of these additive elements.

To examine mechanical characteristics of these samples at normal temperature and 200 OC as operating temperature condition, tensile strength test, elongation test and hardness test were conducted on these samples.

The results are shown in Table 2. For the tests, the backing metal was removed from each sample by machining, that is, the sole Al bearing alloy layer was tested. The shape of the test piece conformed to Item 5 of JIS Z 2201.

8

S

fo o 21 4" a' 4 9 9

V

Table 1 anTtooiticn CIE Srp1 sm~le Ompsitin (in byr w.aigt), the kilanoe being Al b Si ISr W Mg Zn C Yh FeC i b 0 Ti V n: 1 15 20 2.

2 15 2.0 2.5 0.7 3 15 1.7 2.0 0.7 0.4 4 13 1.7 2.5 0.7 0.8 13 2.0 2.0 0.7 0.5 -0.3 0.4 0.4 6 13 2.0 3.0 0.03 7 13 2.0 3.0 0.03 0.7 8 13 2.0 3.0 0.03 9 13 2.0 3.0 0.03 13 2.0 3.0 0.03 0.7 11 13 2.0 3.0 0.03 0.7 12 13 2.0 3.0 0.03 0.7 0.5 13 13 2.0 3.0 0.20 0.3 0.05 14 13 2.0 3.0 0.15 0.4 0.05 13 2.0 3.0 0.15 0.3 fo. 16 13 2.0 3.0 0.10 0.5 U. 17 13 2.0 3.0 0.10 0.4 0.05 18 13 2.0 3.0 0.02 0.5 0.05 19 13 2.0 3.0 0.02 0.2 0.05 20 13 2.0 3.0 0.03 0.7 0.3 0.05 21 13 2.0 3.0 0.03 0.7 0.4 0.05 22 13 2.0 3.0 0.03 0.7 0.3 0.05 23 13 2.0 3.0 0.03 0.7 0.5 0.05 24 13 2.0 3.0 0.03 0.7 0.4 0.05 25 13 2.0 3.0 0.03 0.7 0.5 0.05 26 13 2.0 3.0 0.03 0.7 0.05 0.05 27 13 2.0 3.0 0.03 0.7 0.5 0.3 0.04 0.05 28 13 2.0 3.0 0.03 0.7 0.5 0.4 0.05 29 13 2.0 3.0 0.03 0.7 0.3 0.1 13 2.0 3.0 0.03 0.7 0.4 0.3 0.03 0.05 31 13 2.0 3.0 0.03 0.7 0.5 0.4 0.05 0.03 0.1 32 13 2.0 3.0 0.03 0.7 0.4 0.3 0.03 33 13 2.0 3.0 0.03 0.7 0.3 0.03 34 13 2.0 3.0 0.03 0.7 0.3 0.30 0.05 13 2.0 3.0 0.7 0.3 0.20 0.05 36 13 2.0 3.0 0.7 0.4 0.15 0.05 37 13 2.0 3.0 0.7 0.3 0.15 0.05 38 13 2.0 3.0 0.7 050.15 0.05 39 13 2.0 3.0 0.7 0.4 0.10 0.05 13 2.0 3.0 0.7 0.02 0.05 41 13 2.0 3.0 0.7 0.02 0.05 42 13 2.0 3.0 0.7 0.5 0.3 0.03 0.05 43 13 2.0 3.0 0.7 0.5 0.4 -0.03 0.05 44 13 2.0 3.0 0.7 0.3 0.03 0.1 45 13 2.0 3.0 0.7 2.0 0.4 0.03 0.03 0.05 46 13 2.0 3.0 0.7 0.5 0.4 0.03 0.03 0.1 47 131 2.0 3.0 0.7 0.4 0.03 0.03 48 13 2.0 3.0 0.7 0.3 0.03 L49 132.0..130 1 ao 1.05 10.3 10. 1 C 1 1003 -22- 0 0* 0* 0S**

S

*000 5 0 *500 00 S 0 0

S.

50 0* 00 5 S0SS 00 0 0 05 000* 0 0 SO 0

S

0 Table 2 Mechanical characteristics ard baring perfonce of s&Aples Material ccteritics Beain Sple rdress e ticn Anti- Abrasimn- Anti- No. (in Hv) (in kg/nn) (in seizure resistant fatigue 0 0 prprj prq~erty prcperty SNormel 20CPC Ncrl 200°C N l 20C0Co(k/ (mg) (Hrs) tel~ra- ta~ra- taea turI ture ture 1 32.0 10.0 9.5 4.0 22.0 21.0 120 2.5 2 35.0 12.0 10.0 4.8 18.0 18.5 125 2.5 120 3 39.5 19.0 12.0 5.0 8.5 15.2 150 2.3 150 Qzntrast 4 41.1 18.5 11.8 5.1 17.7 17.0 145 2.3 150 samples 43.8 20.5 12.0 5.2 14.0 14.7 160 2.4 170 6 37.7 15.0 10.3 5.0 23.1 24.5 170 2.0 200 7 39.5 17.1 12.1 5.8 20.0 20.2 185 2.0 220 8 38.7 17.5 12.7 5.4 20.8 20.7 190 2.0 210 9 41.5 19.3 12.9 6.1 21.5 22.0 175 1.7 230 39.8 18.6 13.5 7.2 20.3 19.5 180 1.5 250 11 42.0 19.8 15.2 7.3 22.1 18.7 195 1.8 270 12 45.5 21.3 14.2 6.6 21.4 19.7 200 1.0 250 13 40.7 20.6 13.0 6.1 19.6 18.2 250 1.0 250 14 42.1 20.3 15.2 7.7 21.2 20.7 275 1.0 250 15 43.8 21.0 14.1 7.0 22.3 20.6 270 1.0 265 16 41.4 20.7 13.8 6.9 19.8 21.2 260 1.0 255 17 42.7 24.1 13.8 6.0 20.7 25.4 245 1.2 240 18 43.6 23.8 13.5 5.9 19.9 22.3 300 1.3 250 19 45.0 21.7 12.1 5.8 21.5 19.6 270 1.8 270 20 48.8 25.5 13.4 6.1 20.1 18.7 260 1.7 260 21 45.1 21.4 15.7 7.3 22.3 19.2 280 1.0 230 22 44.7 22.0 14.7 7.0 23.1 18.1 255 1.0 250 23 46.1 23.4 14.8 7.1 23.2 19.9 325 1.5 240 24 48.3 22.6 15.2 6.2 20.8 20.7 285 1.1 230 25 47.7 25.3 14.3 7.4 24.5 22.1 205 1.2 230 26 46.4 24.4 14.8 7.5 22.0 20.8 305 1.3 230 27 47.3 21.9 14.7 7.6 17.2 16.0 275 1.7 250 Sample 28 46.5 25.0 14.6 6.4 18.7 15.8 250 1.6 275 aoring 29 45.2 24.3 15.6 8.0 16.2 18.8 280 1.9 270 to the 30 49.8 23.7 16.9 7.2 16.6 16.1 330 1.0 265 inventiai 31 48.7 26.0 15.5 6.9 15.0 17.3 325 1.0 240 32 46.6 25.1 14.0 7.1 16.0 16.1 285 1.0 230 33 49.2 23.8 15.2 7.0 17.8 18.4 270 1.2 270 34 43.9 22.0 13.8 6.3 18.1 17.1 295 1.1 275 35 48.0 25.6 13.3 6.3 20.8 18.6 260 1.7 260 36 45.5 21.5 15.6 7.5 22.2 19.6 280 1.0 230 37 44.2 22.5 14.4 7.2 23.5 18.7 255 1.0 250 38 46.0 23.3 14.2 7.0 23.3 19.8 325 1.5 240 39 48.1 22.2 15.1 6.0 20.3 20.2 285 1.1 230 40 45.7 26.0 14.5 7.3 24.2 23.1 235 1.1 235 41 43.8 24.5 14.5 7.4 23.0 20.9 320 1.2 235 42 42,3 23.0 14.2 7.4 20.0 17.1 280 1.6 250 43 46,6 25.4 14.4 6.2 18.3 15.4 250 1.6 275 44 45.4 24.5 15.8 8.2 16.5 18.3 280 1.9 270 49.0 23.8 16.9 8.0 16.8 16.8 330 1.0 265 46 49.1 27.0 15.9 6.5 16.0 17.4 330 1.1 250 47 48.1 25.3 14.2 8.2 18.1 17.1 290 1.0 255 48 50.0 28.1 15.5 8.3 18.0 19.5 275 1.1 275 49 45.2 23.0 13.4 6.4 19.4 18.2 290 1.1 275 23

I

h.

r It will be seen from these results that with Samples No. 6 to No. 49 the mechanical strength at high temperature (200 0 C) was less reduced compared to contrast samples. This indicates improvement of the mechanical strength and elongation owing to spherical shape of the Si precipitate due to Sr and Sb.

To examine the anti-seizure property and abrasionresistant property of the samples, tests were conducted by using friction and abrasion machine. The test conditions were as follows.

Frictional speed: 4m/sec.

Counterpart member: S45C, hardness H, C surface roughness 0.8 to 1.OS Lubricant used: SAE, 20w S" *15 Lubricant temperature:150± Seizure load: The surface pressure was increased for every 15 minutes at an interval of 10 kg/cm 2 from 100 kg/cm Seizure load is the surface pressure, with which seizure took place.

20 Abrasion-resistant property: The abrasion-resistant 0e00 property was tested at 100 kg/cm 2 for 6 hours, and the subsequent change in weight was measured.

The results are shown in Table 2.

,j Samples No. 6 to No. 49 show satisfactory anti- 25 seizure property and abrasion-resistant property compared to the contrast samples. Further, it will be seen that the surface performance is improved by addition of Sr and Al matrix reinforcement elements. It will be seen that 24 r .I~ the alloys according to the invention have excellent lubrication function.

Then, each sample was processed into the shape of a bearing, and fatigue test on the final bearing was conducted. The results are shown in Table 2. In this test, like the actual engine condition, the bearing is secured to a connecting rod, and an eccentric load is applied to the rotary shaft for duration test under the following conditions. The duration, during which the performance was maintained without seizure or rupture, was tested.

Surface pressure: 600 kgf/cm 2 Revolving rat 4,000 r.p.m Counterpart material: FCD 70, roughness 0.8 to 15 Lubricant used: SAE 20w .Lubricant temperature: 150 5 °C The upper limit of the test time was set to 300 hours. The average value for N 5 is shown in Table 2.

With the samples according to the invention the duration 20 time is long compared to that of the contrast examples.

fo. Thus, it will be seen that the invention has excellent anti-fatigue property.

Sample No. 7 was obtained by adding 0.03% of Sr to the alloy composition of Contrast Sample 2. The Si precipitate in this case is as shown in Fig. 6. The Si precipitate of Sample No. 36 containing 0.03% of Sb is as shown in Fig. 7. The Si precipitate of Contrast Sample No. 2 is as shown in Fig. 8. Figs. 6 to 8 are 25 i Imicroscopic photographs of the composition of the bearing alloys. The microscopic photograph of each sample was taken after deeply etching it until the shape of Si precipitate particles can be seen. As is apparent from Figs. 6 and 7, with the samples containing Sr and Sb Si prcipitate particles 4 have spherical or rounded shape, and Sn-Pb alloy particles 3 are precipitated in the vicinity of the Si precipitate. In the contrast sample shown in Fig. 8, Si precipitate particles 11 have rodlike or flaky shape, and Sn-Pb alloy particles 3 are spaced apart from the Si precipitate.

EXAMPLE 2 Sample No. 34 containing Sr and Sample No. 49 containing Sb were tested to obtain impact value for 15 comparison with Contrast Sample No. 5 (not containing Sr and Sb) shown in Table 1.

The test was carried out by forming and testing No.

C.

3 test piece (n 5 according to Charpy impact test process indicated at JIS Z 2242.

20 With Contrast Sample No. 5 the average value was 0.84 kg.m/cm 2 with Sample No. 34 the average value was 3.12 kgm/cia 2 and with Sample No. 49 the average value was 3.20 kg.m/cm 2 Obviously, improved effect can be recognized with the bearing alloys containing Sr and Sb according to the invention.

EXAMPLE 3 Table 3 shows samples according to the invention. In these samples, components are contained in the 26 neighboihoc of the upper and lower limits of the ranges according to the invention.

From each sample a forged billet was produced by the method as described before in connection with Example 1.

The forged billet thus produced was press bonded to a backing metal to obtain a bearing material.

To confirm the effects of the invention contrast samples which contain neither Sr nor Sb were produced, and the effects according to the invention were observed by using a microscope.

With the samples containing Sr or Sb according to the invention the Si precipitate particles has round shape close to the sphere. It was confirmed that Sn-Pb I alloy precipitate particles were found adjacent to the Si 15 precipitate. It was thus confirmed that the effect according to the invention can be obtained within the content ranges according to the invention.

In this example, Cu was used as typical element.

Table 3 9 5 59

S

9*559* Sample No. Composition (in by weight) thebalance bein Al Sn Pb Si Sr S Cu 5 0.3 0.5 0.1 51 20 4 5 0,2 52 30 7 10 0.02 0.1 53 5 0.3 0.5 0.05 1 54 20 4 5 0.07 30 7 10 0.02 0.1 56 20 4 5 0.2 0.1 27 i UL- I 1 1 i-~I-

Claims

1. A predominantly aluminum alloy composed of, in addition to Al and any impurities, 3 to 35% w/w Sn, to 10% w/w Si, 0.1 to 10% w/w Pb, at least one member of the group consisting of 0.01 to 0.3% w/w Sr and 0.01 to 0.3% w/w Sb and, optionally, 0.1 to 4% w/w in total of at least one member of the group consisting of Cu, Mg, Zn, Cr, Mn, Fe, Ni, Co, Mo, Ti, V and Zr, at least part of said Si being dispersedly precipitated in a matrix consisting substantially of Al as Si precipitate too particles having spherical or oval shape or a shape having rounded ends and projecting from the surface of the matrix, said Sn and Pb being precipitated as Sn-Pb alloy precipitate in the matrix adjacent to said Si precipitate particles.

2. A predominantly aluminum alloy according to claim 1 in which at least one member of the group consisting of Cu, Mg and Zn is present in an amount of 0.3 to 3% w/w in S* total.

3. A predominantly aluminum alloy according to claim 2, in which at least one member of a group consisting of Cr, Mn, Fe, Ni, Co, Mo, Ti, V and Zr is present in an amount of 0.01 to 1.0% w/w in total.

4. A predominantly aluminum alloy according to any one of claims 1 to 3 in which both Sr and Sb are present in an amount totalling no more than about 0.3% w/w. A predominantly aluminum alloy according to claim 1 and substantially as herein described.

Os18s hhspe.08,ndcspe,2 i -29-

6. A predominantly aluminum alloy substantially as herein described with reference to Examples 6 to 56.

7. A two-layer aluminum bearing material comprising a predominantly aluminum alloy according to any one of claims 1 to 6 and a backing metal sheet. Dated this 18th day of September, 1990 NDC COMPANY, LTD. By its Patent Attorneys SDAVIES COLLISON I I e** I I S 900918,phhspe.008,ndc.spe,29 f **ihpe00,dcpe2